The present invention relates to a screw and a driver bit used for the screw. Especially, the present invention relates to a screw having a bit fitting groove that is suitable for both a Phillips screwdriver and a flat blade screwdriver, and a driver bit used for the screw. More specifically, the present invention relates to a screw having a cross groove formed on the top thereof and a driver bit suitable for the screw, which can engage tightly each other so as to realize quick and secure fastening and loosening by constant and appropriate torque transmission, as well as a header punch for manufacture of screws.
Conventionally, a general combination of a screw and a driver bit having a configuration shown in FIGS. 29-32 is known. FIGS. 29 and 30 show a conventional screw having a cross groove, FIG. 31 shows a driver bit for the screw having a cross groove, and FIG. 32 shows a state in which the screw and the driver bit are engaged with each other.
The conventional screw 10 shown in FIG. 29 has a cross groove 12 on the screw head 10a. This cross groove 12 has inclined groove portions 12a extending from the edge portion to the center of the neck portion 12b and a bottom portion with a substantially conical-shaped bottom surface 14 as a gentle slope. Reference numeral 13 denotes tapered wall portions formed between neighboring cross grooves 12. This tapered wall portions 13 abut and engage a blade of a driver bit mentioned below. On a corner portion neighboring each of the inclined groove portions 12a, a tapered connection surface 17a or 17b is formed respectively, which extends from the position of the conical-shaped bottom surface 14 to the opening rim portion of the cross groove 12 at the screw head 10a. These tapered connection surfaces 17a and 17b are also adapted to engage a part of the blade of a driver bit mentioned below.
On the other hand, the conventional driver bit 20 shown in FIG. 31 has blades 22 for engaging the cross groove 12 of the screw 10 and extension blade 22a adapted to the contour of the inclined groove portions 12a extending from the end edge portion of the cross groove 12 toward the center of the screw neck 12b. The reference numeral 23 denotes tapered walls formed on both side surfaces of the blade 22 and the extension blade 22a. This tapered wall 23 abuts and engages the tapered wall portions 13 formed on the cross groove 12 of the screw 10.
The conventional combination of the screw and the driver bit having above-mentioned configuration, as shown in FIG. 32, when the screw 10 engages the driver bit 20, the blades 22 and extension blades 22a of the driver bit 20 fit in the inclined groove portions 12a of the cross groove 12, and the side walls 23 of the blades 22 and extension blades 22a abut the tapered walls 13 of the cross groove 12 of the screw 10. Thus, a desired torque is transmitted to the screw 10 by rotating the driver bit 20. Namely, the screw can be fastened to or loosened from an object.
In addition, a plus-and-minus screw (i.e., a screw with a cross grooved and slotted head) 10 having a configuration shown in FIGS. 33 and 34 is known, for example, as a screw having a fitting grove that can fit both a Phillips(copyright) screwdriver bit and a flat-blade screwdriver bit. As a screwdriver bit that is used for the plus-and-minus screw 10, the Phillips(copyright) screwdriver bit 20 having the configuration shown in FIG. 31 is used. FIG. 35 shows a state in which the plus-and-minus screw 10 and the Phillips(copyright) screw driver bit 20 engage each other.
The plus-and-minus screw 10 has an advantage in that a conventional flat-blade screwdriver can also be used.
Therefore, the conventional plus-and-minus screw 10 shown in FIGS. 33 and 34 has a cross groove, i.e., a fitting groove 12 on the screw head 10a. This fitting groove 12 consists of a pair of linear grooves 12a and 12b crossing in the center of the screw head 10a. One linear groove 12a is adapted to abut and engage the blade of a Phillips(copyright) screwdriver, and the other groove 12b is adapted to abut and engage the blade of a flat-blade screwdriver.
The linear groove 12a includes an inclined groove portions 12a extending from the edge rim portion to the center portion of the screw neck 10b and the substantially conical-shaped bottom surface 14 formed as a gentle slope at the bottom. Both sides of the inclined groove portions 12a is provided with tapered walls 13a having a taper toward the bottom. This tapered wall 13a abuts and engages the blade of the Phillips screwdriver bit as explained below.
In addition, the other linear groove 12b is formed as a horizontal groove (12a) that has a sufficient width and depth for abutting and engaging the blade of the flat-blade screwdriver bit. Both sides of the horizontal groove 12a is provided with vertical walls 13b that extend substantially vertically toward the bottom. This vertical wall 13b abuts and engages the blade of the conventional flat-blade screwdriver bit.
The corner portions between the linear groove (the inclined groove) 12a and the other linear groove (the horizontal groove) 12b neighboring thereof are provided with tapered connection surfaces 17a and 17b. A part of the blade of the drive bit mentioned below also abut and engage the tapered connection surfaces 17a and 17b. 
Therefore, the conventional Phillips(copyright) screwdriver bit 20 shown in FIG. 31 has a blade 22 that engages the fitting groove 12 of the plus-and-minus screw 10 and am extension blade 22a extending so as to fit the contour of the inclined groove portions 12a extending from the edge portion of the fitting groove 12 to the center portion of the screw neck 10b. The reference numeral 23 denotes the tapered wall portions formed at both side surfaces of the blade 22 and extension blade 22a. Namely, this tapered wall portion 23 abuts and engages the tapered wall 13a formed on one of the inclined groove portions 12a of the fitting groove 12 of the plus-and-minus screw 10.
According to the combination of the conventional plus-and-minus screw and the Phillips(copyright) screwdriver bit, as shown in FIG. 35, when the plus-and-minus screw 10 and the Phillips screwdriver bit 20 are engaged with each other, the blades 22 and the extension blade 22a of the Phillips(copyright) screwdriver bit 20 fit in the fitting groove 12 as mentioned above. One of the pair of the blade 22 and the tapered wall 23 of the extension blade 22a abuts the tapered wall 13a formed on one of the inclined groove portions 12a of the plus-and-minus screw 10. Thus, when the Phillips(copyright) screwdriver bit 20 is rotated, a desired torque is transmitted to the plus-and-minus screw 10. Namely, the plus-and-minus screw 10 can be fastened to or loosened from an object.
However, according to the combination of the conventional screw (the plus-and-minus screw) 10 and the driver bit (the Phillips(copyright) screwdriver bit) 20, as shown in FIG. 32 (FIG. 35), the cross groove 12 of the screw head 10a has an inclined groove portions 12a extending from the edge portion to the center of the screw neck 10b. On the other hand, the corresponding driver bit 20 is adapted so that the edge line portion of the extension blade 22a fit to the contour of the inclined groove portions 12a to engage the cross groove (the fitting groove) 12. In addition, the width of the edge line portion of the extension blade 22a increases little by little from the front to the rear.
Furthermore, since the tapered wall 23 formed on each blade 22 of the driver bit 20 also abuts and engages the tapered wall 13 formed on the cross groove 12 (the inclined groove portions 12a) of the screw (the plus-and-minus screw) 10, when the driver bit 20 is rotated in a predetermined direction, the contact state of the driver bit 20 with the cross groove 12 (inclined groove portions 12a) is such as a tapered contact in the entire surface. Therefore, the tip of the driver bit 20 has a tendency to come out along the slant surface of the inclined groove portions 12a of the cross groove 12 (as shown with an arrow in FIG. 32). This phenomenon is called a come-out phenomenon.
Especially, the contour of the cross groove (the fitting groove) of the conventional screw, as shown in FIG. 30 (FIG. 34), has the width of the cross groove (the fitting groove) 12 that is relatively larger than the width of the edge line portion of the extension blade 22a of the driver bit 20, for example, in order to make easy engagement of the blade tip of the driver bit 20, while the area of tapered wall 13 (and the vertical wall 13b) and the tapered connection surface 17a, 17b that are formed on the boundary portion between the neighboring cross grooves 12, 12 (between the linear grooves 12a and 12b crossing each other) or on the corners is relatively small. Therefore, when rotating the driver bit 20, the tapered wall 13 (and the vertical wall 13b) and the tapered connection surface 17a, 17b are loaded with much stress, and the tapered wall 13 (and the vertical wall 13b) and the tapered connection surface 17a, 17b will be broken little by little as shown by the hatching portion 15 in FIG. 30 (FIG. 34), if the fastening resistance is large. If the breakage portion (15) is enlarged, the come-out phenomenon of the driver bit 20 occurs frequently, and finally fastening operation becomes impossible.
From the above-mentioned view point, a strong pressure of the driver bit 20 against the screw groove portion 12a is necessary to prevent the come-out phenomenon of the driver bit 20 when rotating the driver bit 20. However, if the object to which the screw is fastened is such as a fine component, the object can be broken or damaged, while there is no problem if the object has a high stiffness like a metal.
In addition, if the come-out phenomenon occurs, abrasion of the tip portion of the bit, i.e., the blade 22 and the extension blade 22a is accelerated, and the abrasion causes more occurrence of the come-out phenomenon and further breakage of the screw groove.
Furthermore, if the excessive force is added to the driver bit 20 to prevent the come-out phenomenon, it becomes difficult to transmit a correct torque to the screw. Namely, the force added to the driver bit 20 my varies depending on an operator. As a result, the fastening torque of the screw may vary.
Still furthermore, if the screw is a tapping screw, a propulsion friction is added to a rotation friction of the screw when the screw is fastened to an object such as a plastic. Therefore, the object is heated so that the hardness of the fastening portion of the object may be lowered, or the object to which the screw is fastened may be broken.
On the other hand, the operation of rotating and pressing the driver bit 20 simultaneously is a difficult and tiresome job for the operator when fastening the screw.
In addition, according to the combination of the conventional screw 10 and the driver bit 20, it is difficult to maintain the state where the axis of the screw is coaxial with the axis of the driver bit when fitting the tip of the bit with the screw groove while performing the rotation of the screw when using a manual or electric tool for fastening the screw. If the axis of the driver bit is inclined from the axis of the screw, the come-out phenomenon will occur frequently, and the screw groove may be broken easily.
Furthermore, the come-out phenomenon and the breakage of the screw groove may occur when loosening the screw, too. In this case, it becomes impossible to remove the screw without partly breaking the object to which the screw is fastened. Especially, when the screw groove is blocked with dust or others, the above-mentioned phenomenon occurs easily.
Therefore, the object of the present invention is to provide a screw, a driver bit and a header punch for manufacture of screw that can prevent the come-out phenomenon of the driver bit effectively by improving the configuration of the groove portion of the cross groove of the screw in the combination of the screw and the driver bit, so as to prevent the breakage of the screw that conventionally occurs, and to perform a correct and quick fastening of the screw normally even if the partial breakage occurs in the cross groove of the screw, so that the operation efficiency can be improved significantly.
In addition, another object of the present invention is to provide a combination of a plus-and-minus screw and a driver bit as well as a header punch for manufacture of screw that can prevent the come-out phenomenon of the driver bit effectively by improving the configuration of the groove portion of the bit fitting groove of the screw in the combination of the plus-and-minus screw and the driver bit, so as to prevent the breakage of the screw that conventionally occurs, and to perform a correct and quick fastening of the screw normally even if the partial breakage occurs in the bit fitting groove of the screw, so that the operation efficiency can be improved significantly.
A screw according to the first invention is characterized in that substantially vertical end wall portions of predetermined depth are formed on an end edge portion of a bit fitting groove on an screw head, non-planar bottom portions are raised from lower edge portions of the vertical end wall portions toward the center of the screw head, inclined groove portions are formed extending from the raised portions of the non-planar bottom portions toward the center of the screw neck, a substantially conical-shaped bottom surface is formed on the bottom of the groove, and the bit fitting groove is adapted to a driver bit that has a blade fitting in the bit fitting groove and abutting to the non-planar bottom portions at the lower edge.
In this case, the bit fitting groove in which the blade of the Phillips screwdriver bit fits can be formed as a groove whose width is enlarged little by little from the center of the screw head to the outer portion in the radial direction, so that the angle between the opposing side walls of the neighboring grooves is a little smaller than 90 degrees.
A driver bit that is adapted to the screw is characterized in that a tip potion of the bit has a flat blade provided with substantially vertical end edge portions fitting in along the vertical end edge portion of the bit fitting groove of the screw head, and the tip edge surface of the blade is substantially horizontal surface with a protrusion formed at the center of the horizontal surface.
In this case, if the bit fitting groove of the screw, in which the blade of the Phillips screwdriver bit fits, is formed as the groove whose width is enlarged little by little, the driver bit adapted to the screw preferably has the flat blade whose tip portion has side walls of the shape adapted to the groove whose width is enlarged little by little forming the bit fitting groove of the screw.
In addition, each end edge portion of the flat blade has the right-angled edge or an acute-angled edge crossing the horizontal surface of the blade tip and protruding a little in the horizontal surface side.
Furthermore, the protrusion formed at the center of the horizontal surface of the flat blade can be formed in the shape that is adapted to the inclined groove portions and the conical-shaped bottom surface formed at the center of the bit fitting groove of the screw.
A header punch for manufacture of the screws includes protrusions for forming the vertical edge wall portions of the bit fitting groove of the screw head and forming the non-planar bottom portions raised from the lower edge portion of the vertical edge wall portion toward the center of the screw head. The header punch also includes protruding lines for forming grooves extending with inclined or curved from the protrusion toward the center of the screw neck.
If the bit fitting groove of the screw is formed as the groove whose width is enlarged little by little, side walls of the protrusion for forming the bit fitting groove are preferably shaped to be adapted to the groove whose width is enlarged little by little.
According to the screw of the first invention having the above-mentioned configuration, substantially vertical end wall portions of predetermined depth are formed on an end edge portion of the bit fitting groove on an screw head, non-planar bottom portions are raised from lower edge portions of the vertical end wall portions toward the center of the screw head, inclined groove portions are formed extending from the raised portions of the non-planar bottom portions toward the center of the screw neck. Therefore, concerning the engagement of the blade tip of the driver bit with the bit fitting groove, a contact area of the tapered contact with the entire bit fitting groove is small. In addition, since the non-planar bottom surface is formed so that the area of the wall portions that the tip of the driver bit abuts at the boundary portion where the neighboring bit fitting grooves cross each other is enlarged, the come-out phenomenon of the driver bit is prevented securely.
In addition, the driver bit of the first invention includes a tip potion having a flat blade provided with substantially vertical end edge portions fitting in along the vertical end edge portion of the bit fitting groove of the screw head, and the tip edge surface of the blade is substantially horizontal surface with a protrusion formed at the center of the horizontal surface. Therefore, the driver bit that is the most adapted to the screw is provided.
Furthermore, the screw of the first invention can be manufactured easily by using the header punch having the protrusion and the protruding lines that are adapted to the contour of the bit fitting groove.
A plus-and-minus screw of the second invention has a bit fitting groove of a cross groove formed in the screw head. One of crossing linear grooves making up the bit fitting groove is formed so as to be adapted to a blade of a Phillips screwdriver bit, while the other linear groove is formed so as to be adapted to a blade of a flat-blade driver bit. The plus-and-minus screw of the first invention is characterized in that substantially vertical wall portions having predetermined depth are formed at the end edge portion of the linear groove adapted to the blade of the Phillips screwdriver bit, and the bit fitting groove is formed so as to be adapted to a driver bit having a blade that fits in one of the linear grooves and abuts the bottom of the groove at the lower edge when the blade tip of the Phillips screwdriver bit engages the bit fitting groove.
In this case, the bottom portion of one of the linear groove adapted to the blade of the Phillips screwdriver bit can have inclined groove portions extending from the lower edge of the vertical edge wall formed at the end edge portion of the groove toward the center of the screw head and a substantially conical-shaped bottom surface formed at the center bottom.
In addition, the bottom portion of one of the linear grooves can have a non-planar bottom portion raised from the lower edge of the vertical edge wall formed at the end edge portion of the linear groove toward the center of the screw head, inclined groove portions that extends from the raised portion of the non-planar bottom portion toward the center of the screw head, and a substantially conical-shaped bottom surface formed at the center bottom portion thereof.
Furthermore, the bottom portion of one of the linear groove can be formed as an inclined bottom surface inclined downward from the end edge portion of the of the vertical edge wall formed at the end edge portion of the groove toward the center of the screw neck, and a substantially conical-shaped bottom surface can be formed at the center bottom.
Furthermore, the bit fitting groove that the blade of the Phillips(copyright) screwdriver bit fits in and engages can have linear grooves, one of which is formed as a groove whose width is enlarged little by little from the center of the screw neck to the outer portion in the radial direction, and the width of the other linear groove is widened little by little from the center of the screw neck to the outer portion in the radial direction, so that an angle between the opposing wall portions of the neighboring grooves can be a little smaller than 90 degrees.
On the other hand, a driver bit adapted to the above-mentioned plus-and-minus screw is characterized in that a flat blade having substantially vertical end edge portions fitting in along the vertical wall portions of the linear groove of the screw head is provided to the tip portion, and the tip edge surface of the blade is substantially horizontal surface with a protrusion formed at the center of the horizontal surface.
If the bit fitting groove of the screw is formed as the groove whose width is enlarged little by little, the driver bit adapted to the screw preferably has the flat blade whose tip portion has side walls of the shape adapted to the groove whose width is enlarged little by little forming the bit fitting groove of the screw.
In addition, each end edge portion of the flat blade of the driver bit preferably has the right-angled edge or an acute-angled edge crossing the horizontal surface of the blade tip and protruding a little in the horizontal surface side.
Furthermore, the protrusion formed at the center of the horizontal surface of the driver bit is preferably formed in the shape that is adapted to the inclined groove portions and the conical-shaped bottom surface formed at the center of the bit fitting groove of the plus-and-minus screw.
A header punch for manufacture of the plus-and-minus screws includes protrusions crossing each other for forming the vertical edge wall portion of the bit fitting groove of the screw head and forming a predetermined groove bottom portion extending from the lower edge portion of the vertical edge wall portion toward the center of the screw head. The header punch also has protruding lines for forming the grooves extending with inclined or curved from the protrusions toward the center of the screw neck.
If the bit fitting groove of the screw is formed as the groove whose width is enlarged little by little, side walls of the protrusions for forming the bit fitting grooves are preferably shaped to be adapted to the groove whose width is enlarged little by little.
According to the plus-and-minus screw of the second invention having the above-mentioned configuration, substantially vertical end wall portions of predetermined depth are formed on an end edge portion of the bit fitting groove made of one of the linear grooves on an screw head. Therefore, concerning the engagement of the blade tip of the Phillips(copyright) screwdriver bit with the bit fitting groove, a contact area of the tapered contact with the linear groove is partial and small. In addition, since a bottom portion of the bit fitting groove is formed so that the area of the wall portions that the tip of the driver bit abuts is enlarged, the come-out phenomenon of the driver bit is prevented securely.
In addition the driver bit of the second invention includes a tip potion having a flat blade provided with substantially vertical end edge portions fitting in along the vertical end edge wall portion of the bit fitting groove consists of one of the linear grooves on the screw head, and the tip edge surface of the blade is substantially horizontal surface with a protrusion formed at the center of the horizontal surface. Therefore, the driver bit that is the most adapted to the plus-and-minus screw is provided.
Furthermore, the screw of the second invention can be manufactured easily by using the header punch having the protrusions and the protruding lines that are adapted to the contour of the bit fitting groove, especially one of the linear grooves.
Furthermore, a driver bit for a plus-and-minus screw of a third invention is a driver bit for a plus-and-minus screw adapted to a plus-and-minus screw having a bit fitting groove formed by a pair of linear grooves consist of an inclined groove portion and a horizontal groove portion crossing each other at the center of the screw head. The driver bit for a plus-and-minus screw is characterized in that the driver bit has a flat blade with an inclined end edge portions fitting in along the inclined groove portions of the plus-and-minus screw, and another flat blade crossing the flat blade perpendicularly to fit in along the horizontal groove of the plus-and-minus screw, and has a horizontal end edge portion extending substantially perpendicularly and abutting the bottom portion of the horizontal groove. The center portion of the tip of each blade is provided with a protrusion that fit in the conical-shaped bottom surface formed in the center of the screw head of the plus-and-minus screw.
In this case, the protrusion formed at the tip center of each flat blade can be formed in shape that is adapted to the groove portion and the conical-shaped bottom surface formed at the center of the bit fitting groove of the plus-and-minus screw.
In addition, the flat blade that fits in along the horizontal groove of the plus-and-minus screw and has a horizontal end edge portion extending substantially perpendicularly to abut the bottom portion of the horizontal groove is preferably formed so that the width of the blade is adapted to the width of the horizontal groove.